MyBatis 入門開發

第一: parameterType傳入參數傳遞簡單數據類型

<select id="findUserById" parameterType="int" resultType="cn.fy.domain.User">
    SELECT id,username,birthday,sex,address  FROM USER WHERE id = #{id}
    </select>

傳遞pojo對象

<!—傳遞pojo對象綜合查詢用戶信息 -->
    user 使用了別名.
    <select id="findUserByUser" parameterType="user" resultType="user">
       select * from user where id=#{id} and username like ‘%${username}%‘
    </select>

    #{id} : 使用 user中的id
    ${username}:使用user中的username.
    // 如果參數類型user 中有屬性 order 類
    <select id="findUserByUser" parameterType="user" resultType="user">
       select * from user where id=#{order.id} and username like ‘%${username}%‘
    </select>
 

mybatis可以通過ognl 表達式: #{屬性.屬性.屬性}
傳遞hashmap

map綜合查詢用戶信息 -->
    <select id="findUserByHashmap" parameterType="hashmap" resultType="user">
        select * from user where id=#{id} and username like ‘%${username}%‘
    </select>

     @Test
    public void findUserByHashmap() {
        SqlSession session = MyBatisUtil.getSession();

        UserMapper userMapper = session.getMapper(UserMapper.class);
        //構造查詢條件Hashmap對象
        HashMap<String, Object> map = new HashMap<String, Object>();
        map.put("id", 1);
        map.put("username", "張");
        //傳遞Hashmap對象查詢用戶列表
        List<User>list = userMapper.findUserByHashmap(map);
        //關閉session
        session.close();
    }

    select * from user where id=? and username like ‘%管理員%‘
 

第二: resultType(輸出類型)輸出簡單類型

select count(1) from user Public void testFindUserCount() throws Exception{ //獲取session SqlSession session = sqlSessionFactory.openSession(); //獲取mapper接口實例 UserMapper userMapper = session.getMapper(UserMapper.class); User user = new User(); user.setUsername("管理員"); //傳遞Hashmap對象查詢用戶列表 int count = userMapper.findUserCount(user); //關閉session session.close(); } 輸出簡單類型 select * from user where id = #{id} Public void testFindUserById() throws Exception { //獲取session SqlSession session = sqlSessionFactory.openSession(); //獲限mapper接口實例 UserMapper userMapper = session.getMapper(UserMapper.class); //通過mapper接口調用statement User user = userMapper.findUserById(1); System.out.println(user); //關閉session session.close(); } 輸出pojo列表 select * from user where username like ‘%${value}%‘ @Test public void dimFind() { SqlSession session = MyBatisUtil.getSession(); List list = session.selectList("test1.findUserByUsername", "常山"); System.out.println(list); } 輸出hashmap select username,sex from user @Test public void findUserNameAndSex() { SqlSession session = MyBatisUtil.getSession(); UserMapper userMapper = session.getMapper(UserMapper.class); //構造查詢條件Hashmap對象 // 傳遞Hashmap對象查詢用戶列表 // 註意不能返回HashMap,還是要返回list List list = userMapper.findUserNameAndSex(); System.out.println("--list-" + list); //關閉session session.close(); } --list-[{sex=2, username=王五}, {sex=1, username=張三}, {sex=1, username=張小明}] resultMap resultMap 替代 resultType. ``` resultType可以指定pojo將查詢結果映射為pojo，但需要pojo的屬性名和sql查詢的列名一致方可映射成功。 如果sql查詢字段名和pojo的屬性名不一致，可以通過resultMap將字段名和屬性名作一個對應關系 ，resultMap實質上還需要將查詢結果映射到pojo對象中。 resultMap可以實現將查詢結果映射為復雜類型的pojo，比如在查詢結果映射對象中包括pojo和list實現一對一查詢和一對多查詢。 ``` SELECT id,username,birthday,sex,address FROM USER WHERE id = #{id} -------------------------------- @Test public void findUserResultMap() throws Exception { SqlSession session = MyBatisUtil.getSession(); UserMapper userMapper = session.getMapper(UserMapper.class); //構造查詢條件Hashmap對象 List list = userMapper.findUserResultMap(10); //--list-[User{id=10, username=‘張三‘, sex=‘1‘, birthday=Thu Jul 10 00:00:00 CST 2014, address=‘北京市‘}] System.out.println("--list-" + list); //關閉session session.close(); }

MyBatis 入門開發 —-輸入,輸出參數